Global benchmark shows that existing Earth system models underestimate vulnerability of soils to increased temperature.
DOE supported researchers combined global maps of productivity, soil carbon, and environment to demonstrate a basic pattern of environmental controls on soil decomposition, which is that soil carbon temperature sensitivity is highest in cold regions. From this, they derived a theory to explain the pattern as an outcome of the scaling of soil freeze-thaw processes in time and depth, and apply the benchmark to existing ESMs and newer land modeling approaches.
The study shows via a global benchmark, that existing models systematically underestimate the temperature sensitivity of soil carbon decomposition, and that the solution to this underestimation is to take into account the way in which surface soils freeze.
The results show that the sensitivity of soil carbon to temperature is highest in cold climates, even for surface rather than permafrost layers, and that this global pattern can most simply be explained as an outcome of the way in which soils experience freeze-thaw processes. The team also show that all existing (CMIP5-era) ESMs systematically underestimate this temperature sensitivity, whereas newer approaches such as the CLM4.5 representation that forms the basis of the E3SM soil biogeochemistry, can match observations. Thus, our approach shows two major impacts: (1) that the single most important relationship that soil models must consider is the physical scaling of freeze and thaw and (2) existing estimates systematically underestimate the long-term temperature sensitivity of surface soil carbon.
Contacts (BER PM)
Staff Scientist, Lawrence Berkeley National Laboratory
CDK received support from the Regional and Global Climate Modeling program through the BGC-Feedbacks SFA and the Terrestrial Ecosystem Sciences and Earth System Modeling programs through the Next Generation Ecosystem Experiments-Tropics (NGEE-Tropics) project of the Biological and Environmental Research (BER) Program in the U. S. Department of Energy Office of Science.
Koven, C. D., et al. “Higher Climatological Temperature Sensitivity of Soil Carbon in Cold Than Warm Climates.” Nature Climate Change 7, 817-822 (2017). [DOI: 10.1038/NCLIMATE3421]. (Reference link)
SC-23.1 Climate and Environmental Sciences Division, BER
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